Patent GB-796181-A (GB)
Title: Dithiophosphate esters and salts thereof and lubricating compositions containing them
IPC: C07F9/165
Filed: 1955-10-12
Abstract: A dithiophosphate triester is obtained by reacting a dithiophosphate having the formula [(RO)2P(S)-S]xY, wherein R is an hydrocarbon radical containing 3 to 20 carbon atoms, Y is hydrogen or a metal of Group I or II, e.g. sodium, potassium, calcium, barium, magnesium or zinc, and x is the valency of Y, with an alkylene oxide containing 2 to 18 carbon atoms or with 1 to 3 mols. of a glycol containing 2 to 18 carbon atoms.  The preferred proportion of alkylene oxide is also 1 to 3 mols. per mol. of dithiophosphate.  The reaction may be effected at 70 DEG  to 400 DEG  F., preferably 100 DEG  to 300 DEG F., and at atmospheric pressure or pressures up to 10 atmos.  The reaction is substantially completed in 0.5 to 5 hours.  The dithiophosphatealkylene oxide or glycol reaction product may be further reacted with P2S5, and 1 mol. of the product so formed may be reacted with 1 to 3 mols. of alkylene oxide or glycol to give a second reaction product; a third product may be obtained by reacting the second product with more P2S5; and a fourth product may be obtained by reacting the third product with 1 to 3 mols. of additional alkylene oxide or glycol.  All of the above-described products are useful as synthetic lubricating oils, (see Group III). The reactions are preferably effected at 100-300 DEG  F. for 0.5 to 10 hours, generally 2 to 6 hours.  The dithiophosphate starting materials are prepared by reacting an alcohol or a mixture of alcohols with P2S5 at 150 DEG  to 300 DEG  F. for 2 to 10 hours. Suitable alcohols are cyclohexanol, isopropanol, 2-ethylhexanol, capryl alcohol, n-butanol, oleyl alcohol, stearyl alcohol and methyl isobutyl carbinol.  Oxo alcohols such as C 8oxo alcohol from butylene-propylene copolymer, C2 oxo alcohol from tripropylene, and C13 oxoalcohol from tetrapropylene, are also suitable.  Specific examples of dithiophosphates which may be employed in the invention are zinc dihexyl dithiophosphate, zinc hexyl octyl dithiophosphate, barium isopropyl octyl dithiophosphate, sodium butyl tetradecyl dithiophosphate, dioctyl dithiophosphoric acid, calcium didodecyl dithiophosphate, potassium nondecyl pentadecyl dithiophosphate, hexyl decyl dithiophosphoric acid, zinc isopropyl methylisobutylcarbinyl dithiophosphate, and magnesium cyclohexyl amyl dithiophosphate. Specific examples of alkylene oxides are 1,2-propylene oxide, 1,3-propylene oxide, 1,2-butylene oxide, ethylene oxide, 1,2-hexylene oxide, 2,3-amylene oxide, 1,2-decylene oxide, 2,3-octadecylene oxide and 2,3-octylene oxide. Specific examples of glycols are 1,2-propylene glycol, 1,3-propylene glycol, ethylene glycol, 1,2-butylene glycol, 2,3-butylene glycol, tetradecylene glycol, 1,2-amylene glycol, 3,4-hexylene glycol, 1,2-dodecylene glycol, 1,2-octalene glycol and 1,2-octadecylene glycol.  It is convenient to add the alkylene oxide or glycol to the dithiophosphate, and the latter may be dissolved initially in an inert solvent such as a mineral lubricating oil.  In examples: (I) (A) zinc di-[2-(41-methylpentyl)]-dithiophosphate in a diluent mineral oil is reacted with propylene oxide; (B) barium di-[2-(41-methylpentyl)] in oil solution together with barium sulphonate is reacted with propylene oxide; (C) a C8 oxo alcohol obtained from a mixture of isomers of hexene is treated with P2S5 to form a di-C8 oxo dithiophosphoric acid and the latter is then reacted with propylene oxide; (D) the di-8C-oxo dithiophosphate of (C) is reacted with zinc oxide to form the zinc salt which is then reacted with propylene oxide; (E) the di-C8 oxo dithiophosphoric acid of (C) is reacted with propylene oxide; (F) the product (E) is reacted with P2S5; (G) the product (F) is reacted with further propylene oxide; (H) di-isopropyl dithiophosphoric acid is prepared by reacting isopropyl alcohol with P2S5 for 2 hours at 180 DEG  F.; the product is then reacted with propylene oxide; (I) the zinc di-[2(41-methylpentyl)]-dithiophosphate of (A) is reacted with 1,2-propylene glycol.ALSO:Lubricating oil compositions comprise a major proportion of a mineral or synthetic lubricating oil and from 0.1 to 10 per cent, preferably 0.5 to 5 per cent, by weight, based on the total composition, of a compound obtained by reacting a dithiophosphate having the formula [(RO)2 P(S)-S]xY, wherein R is a hydrocarbon radical containing 3 to 20 carbon atoms, Y is a hydrogen atom or a metal of Groups I and II, and x is the valency of Y, with an alkylene oxide containing 2 to 18 carbon atoms, or 1 to 3 mols. of a glycol containing 2 to 18 carbon atoms.  [For preparation see Group IV (b)] It is convenient to prepare concentrated oil solutions in which the amount of additive ranges from 25 to 50 per cent by weight and to prepare the lubricating oil composition by blending the concentrate with the base oil. The additives may be employed in compositions containing metal soaps, metal petroleum sulphonates, metal phenates, alcoholates, alkyl phenol sulphides, organo phosphates, phosphites, thiophosphates, and thiophosphites, metal xanthates, thioxanthates, and thiocarbamates.  Alkyl phenols and phenol sulphides may also be present.  The base oil may be a mineral oil. Hydrogenated oils, white oils or synthetic oils, e.g. prepared by polymerization of olefins, by reaction of oxide of carbon with hydrogen, or by hydrogenation of coal, may also be used.  Other synthetic oils include esters of monobasic or dibasic acids, esters of glycols, complex esters, phosphoric acid esters, halocarbon oils, alkyl silicates, sulphite esters, carbonates, mercaptals, formals, polyglycol type synthetic oils, or mixtures of any of the above.  Suitable examples are indicated.  Animal, vegetable or fish oils or their hydrogenated or volatilized products may be employed in admixture with mineral oils. Other agents such as dyes, pour point depressants, heat-thickened fatty oils, sulphurized fatty oils, sludge dispersers, antioxidants, thickeners, V.I. improvers, oiliness agents, resins and olefine polymers may also be present.  Alcohols having 8 to 20 carbon atoms, e.g. octyl, lauryl, or stearyl alcohol are suitable plasticizers and defoamers.  The additives may also be used in cutting oils, flushing oils, turbine oils, transformer oils, industrial oils, and in greases.  The reaction products of dithiophosphates and alkylene oxides or glycols may be further treated with P2S5 and additional alkylene oxides or glycols [for preparation see Group IV (a)] to give high molecular weight products which are suitable as lubricating oils in lubricating oil compositions.  Generally, when used as the sole lubricant in compositions they are employed in major proportions of about 55 to 95 per cent of the total composition.  They may also be used together with mineral or synthetic lubricating oils in minor proportions of about 5 to 45 per cent by weight of the total composition.  Overall they may be used in any proportions from 1 per cent or less to 99 per cent or more by weight based on the total composition.  In examples, compositions comprising a reaction product of zinc di-[2-(41-methylpentyl)] dithiophosphate and propylene oxide, or a barium di-C8-oxo dithiophosphate-propylene oxide product, in a mineral lubricating oil are evaluated.  Compositions containing a di-C8-oxo dithiophosphoric acid-propylene oxide reaction product and a mineral oil are also described.